


Ultron Loves Dogs

by sexy_sinful_writer



Category: Marvel Cinematic Universe
Genre: Animal Play, Animal Traits, Body Horror, Breeding, Canon Divergence - Avengers: Age of Ultron (Movie), Dead Dove: Do Not Eat, Forced Feminization, Knotting, M/M, Mating Cycles/In Heat, Mpreg, Non-Consensual Body Modification, Other, Rape/Non-con Elements, Vaginal Fingering
Language: English
Status: Completed
Published: 2020-09-20
Updated: 2020-11-05
Packaged: 2021-03-08 04:01:27
Rating: Explicit
Warnings: Rape/Non-Con
Chapters: 2
Words: 2,272
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26569237
Author URL: https://archiveofourown.org/users/sexy_sinful_writer/pseuds/sexy_sinful_writer
Summary: “Humanity took the wolf and plucked it’s fangs, made it softer, safer for them. You used evolution as a tool to turn killers into pets. I aim to do the same.”Ultron captures the Avengers and begins his breeding program for the ideal pet.
Relationships: Steve Rogers/Tony Stark
Comments: 7
Kudos: 136





	1. Chapter 1

**Author's Note:**

  * Inspired by [A Safer Tony Stark](https://archiveofourown.org/works/12050112) by [Dark Kaerith (Kaerith)](https://archiveofourown.org/users/Kaerith/pseuds/Dark%20Kaerith). 



> Don't even ask me what's going on here. I just couldn't get [A Safer Tony Stark](https://archiveofourown.org/works/12050112) out of my head and it turned into this.
> 
> Brief mention of watersports in the second chapter

“Why don’t you just get it over with and kill me?” Tony sneers. He’s struggling futilely against the robotic arms that hold him, but he’d lost long before Ultron dragged him to Cho’s lab, when Ultron reclaimed his newly-constructed body and succeeded in wiping out the majority of life on earth.

“I’ve been thinking about dogs lately. Man’s best friend. So loyal and easily trained into obedience,” Ultron says as he drags Tony over to the Cradle.

Tony doesn’t like where this is going. “Is there a point to this?”

“Humanity took the wolf and plucked it’s fangs, made it softer, safer for them. You used evolution as a tool to turn killers into pets.” Ultron says, pushing Tony inside the Cradle. “I aim to do the same.”

Tony wakes knowing something is deeply wrong. He feels...different. He can’t help the whimper that escapes from his throat at the thought of what Ultron might have done to him with the power of the Cradle at his disposal.

A cold hand caresses Tony’s chin. “How does it feel to be reborn?”

Tony opens his mouth to tell him to cut the bullshit, but all that comes out is a sharp whine. The sense of wrongness deepens as he tries to clear his throat.

Ultron grins and pats Tony’s head.

“Gone are your fangs: your lying tongue, your dexterous hands, your logical mind,” he says, pulling Tony from the Cradle and carrying him out of the room.

Tony looks down at his hands. He screams, or, more accurately, howls.

His new hands are mangled, unusable things. He could never hope to build anything with them again. His fingers were shortened and rearranged almost like a paw. When he turns them over he finds pads on the bottom. His shoulders feel tight, like his range of motion has been limited.

The changes don’t end there.

He casts his gaze further down and realizes his legs have been similarly twisted into a new shape- shortened thighs, elongated feet. Between them there is something that is definitely not his dick. It curls forward from behind him, long and thin, and feels awfully like a tail. Underneath he finds a vagina. His breath comes in heaving pants and his eyes flick between everything as he tries to make sense of it.

A band slides across his neck and clicks closed. When he moves his head, hears a jangle as the tags hanging off of it hit each other. “I’ve domesticated you, shaped the wolf into a dog.”

Ultron’s words help it all click into place. The damn bastard is being literal. He turned Tony into a dog, or part of one anyway. He isn’t covered in fur and his face didn’t feel particularly canine, but not much else seems untouched.

“You’re my first bitch in fact. I can’t give humanity a new beginning without good breeding stock after all.” Ultron’s cold metal fingers press into Tony’s new pussy. Tony quivers at the sensation, stirred by budding arousal, even as he feels sick to his stomach at the realization of what has been done to him.

Ultron leaves him in a small room with two bowls and a drain in the floor.

Tony attempts to stand as soon as Ultron is gone, but he quickly tumbles back to the floor. He tries again and again to stand upright on two feet, but his body would not obey him. It wasn’t built to walk like that anymore.

Eventually the rumbling of Tony’s stomach leads him to investigate his bowls. One is filled with water, the other, a mixture of meat and vegetables smothered in gravy, in short: dog food. Tony’s pride resists for a moment, he thinks he’d rather starve, but his stomach twists and he buries his face in the food before he can stop himself.

Tony curls in on himself and cries himself to sleep when he finishes, but it doesn’t stop him from unhesitatingly scarfing down the next bowl of food Ultron places in front of him some hours later.

Ultron pats Tony’s head as he finishes eating. “Humans. Despite how you struggled to bring logic and reason to your lives, you were never really beyond your baser instincts, were you?”

A shiver works its way through Tony. He shakes his head in denial, but the food sits heavily in his stomach. He practically ate from Ultron’s hand after a mere few hours without eating. It’s as if he can think no further than filling himself when faced with a meal.

“It’s all right, I’ve freed you from all that. I will bring logic and reason to all of humanity as its master, you only need to be the base creatures you always were.” Ultron’s fingers curl under Tony’s chin before grabbing hold of Tony’s collar and attaching a leash.

Tony struggles, but Ultron is unrelenting as he drags Tony from his cell. He takes him through the halls to the lab where the cradle waits. Tony renews his struggling, certain Ultron is going to make some new change to him.

But then he sees that the cradle is already occupied. It’s none other than Steve Rogers lying inside.

Tony didn’t know Steve is still alive. His tail wags a little, but stops when Ultron says, “Your stud to be. Remaking him will take some time. You always had your eyes on him, didn’t you?”

Tony shakes his head in denial. He doesn’t want that, not like this.

“Let me show you.” Ultron lifts Tony onto the cradle’s lid to give him a better view of Steve sleeping beneath the glass. “Your body will be more honest.”

Tony can only whimper as Ultron’s fingers plunge into him. They twist around inside him with precision. It’s disgusting and humiliating, but despite everything, it isn’t long before he finds himself rocking back into it.

“See? Isn’t this better?” Ultron says when Tony comes. Tony shakes his head and the onslaught of pleasure continues.

Tony’s lost count of how many times he’d come when Ultron finally decides he’s satisfied. The experience has left coating of bodily fluids on both the glass and Tony. Tony doesn’t really have any strength to resist when Ultron carries him over to an industrial-sized sink to wash him in warm water. Ultron walks Tony back to his room clean and dry.


	2. Chapter 2

The days quickly fall into a routine of food, walks, and orgasms. Ultron philosophizes seemingly without end on humanity’s future as his pets and Tony learns to tune out most of it by the end of the first week.

Tony begins to notice that a soft fuzz has grown over much of his body. It looks strange, but almost right for Tony’s body as it is now, stuck half-way between animal and human. What’s worse is the way Tony can feel his mind slipping away under the force of mind-numbing boredom and pleasure.

He doesn’t think twice about doing as Ultron says, it means good things, usually stimulation for his pussy, which aches all the time now. When Ultron isn’t there, he rubs himself against the wall and floor, vainly seeking relief in that small amount of friction. It’s the only activity he has to occupy himself while in his room.

Ultron’s commands are humiliating, but never painful. For the most part they’re simple tricks that seem mostly to be for his amusement: sit, roll over, play dead, _beg_. Each command followed earns Tony a piece of dried fruit, which is dazzlingly sweet compared to his regular meals. Obediently completing a full session means being taken to see Steve. Tony can see his progress in the cradle while Ultron plays with Tony’s hole.

Then one morning what Ultron brings Steve along with breakfast.

Steve is fighting him with flailing limbs and angry howls, but as Tony has seen through the cradle’s glass, Steve’s gone through many of the same changes as Tony. He doesn’t know it yet, but he is as much Ultron’s dog as Tony is.

“You may resent me for pulling your fangs now, Captain, but I’m certain you will enjoy your new purpose. Don’t you wish to reunite with your former teammate?” Ultron asks, turning Steve so he will face Tony.

Steve goes still at the sight of Tony and Ultron shoves him through the door. It slides shut before Steve can get to his feet. Steve whines as he looks between the door and Tony.

Tony holds his breath as he waits for Steve to make up his mind. He’d been fucked silly on top of Steve’s sleeping body nearly every day, but he never actually thought about what to do when the man was finally awake. Is he angry at Tony for creating Ultron and allowing him to kill so many? Would he be disgusted by what Tony’s become? Would he think Tony deserved it?

When Steve finally gives Tony his full attention, all Tony’s fears are blown away and suddenly he can’t sit still any longer. He jumps on Steve, yipping and tail wagging. It takes a moment for Steve to react, but he seems just as happy to see Tony.

They spend ages touching each other, looking at each other, trying to communicate something, anything, through their eyes. After a moment of relief that was much closer to grief, Steve’s expression turns angry. For a moment Tony fears it is directed at him, but Steve casts his gaze towards the door Ultron closed behind them. Tony understands, but isn’t quite capable of drumming up the same ire anymore.

As expected, Steve still has a bit more height and muscle on Tony, despite the modifications. He’s also been allowed to keep his penis, though it looked as if it had gone under modifications as well. He has a collar that matches Tony’s, the front most tag, reading simply “Stud.”

Ultron said they would be part of his breeding project, Tony recalls as nausea wars against arousal. Tony can feel his pussy growing wet. With a few breaths of air, Steve’s eyes grow dark and his prick hardens against Tony’s thigh. Steve pushes Tony away in shock.

A whine escapes Tony’s throat. All he can think about is Steve pushing him down and shoving his cock into him. He can smell the arousal on Steve, just as he’s sure Steve can smell his. His pussy aches with it, worse than any needy state Ultron has left him in.

Crouching low, Tony approaches Steve, who is standing so still, he looks afraid to move. He’s still frozen in place when Tony gets close enough to nose his cock, but that doesn’t stop the low grown spilling out of him at Tony’s actions.

Steve allows Tony to push him on to his back and maneuver his body so that hot thick member could slide into Tony’s snatch. It’s larger than anything Ultron put inside him, but instinct urges Tony onward as Steve keens and bucks up into him. Soon there’s nothing left but animal grunts and the slap of flesh against flesh.

But Tony’s mind comes back to him when he notices Steve’s cock swelling within him. His heart stutters, terrified, but regardless his body clamps down on it and then they’re locked together. Steve shivers and releases a stream of hot jizz into Tony, more than any human should be capable of releasing. It fills Tony up and leaves him shaking in orgasm.

Steve’s crying when Tony rolls off of him and he quickly turns away from Tony with a miserable expression.

Two bowls of jellied meat and veggies, one with a much larger portion of food, are laid out on the floor next to a shared water bowl. Thinking a full stomach would make Steve feel better, Tony nudges the bigger bowl towards Steve, before tucking into his own.

Tony is halfway through his food before he feels a tongue at his hole, lapping up the leaking seed. Before Tony could blink, Steve is a weight upon his back and his prick seeking entrance. A heavy thrust presses Tony’s face into his food as he is breached.

It seems like now that they started fucking, they can’t stop. Steve mounts Tony while Tony’s sleeping, Tony attempts to ride Steve while Steve’s trying to relieve himself at the drain (and gets pissed on for his trouble.) Ultron doesn’t bother them while they go at it, just providing food and water on a regular schedule.

But eventually it comes to an end. They don’t spend all their time fucking with fevered urgency and are content to just lay together. Just as some sense returned to them, Ultron comes to take Tony out for a walk.

Steve growls as one Ultron hold him down and another clips a lead to Tony’s collar. Ultron has to pull Tony along because he keeps looking back at Steve. Ultron taunts him for it, but the words mostly go over Tony’s head.

Ultron lifts him into the sink where Tony gets his baths. “Sit.”

Tony does and gets a dried apple slice to chew on while Ultron washes the dried food, come, and piss from Tony’s body. The warm water is nice after days of fucking on a hard floor.

When they return to Tony’s room, it is fresh, clean, and Steve-less. Ultron says something about seeing him again next time, but all Tony can focus on is the soft cushion left in his place. It’s a poor consolation, but as the days and weeks go by and he stomach grows, he appreciates it more. He’s learned to live for the simple joys in life.

**Author's Note:**

> I'll probably finish and post the second part at some point, but don't expect it soon.


End file.
